U.S. patent number 7,508,504 [Application Number 11/891,657] was granted by the patent office on 2009-03-24 for automatic wafer edge inspection and review system.
This patent grant is currently assigned to Accretech USA, Inc.. Invention is credited to Paul F. Forderhase, Zhiyan Huang, Ju Jin, Siming Lin, Michael D Robbins, Satish Sadam, Vishal Verma.
United States Patent |
7,508,504 |
Jin , et al. |
March 24, 2009 |
Automatic wafer edge inspection and review system
Abstract
A substrate illumination and inspection system provides for
illuminating and inspecting a substrate particularly the substrate
edge. The system uses a light diffuser with a plurality of lights
disposed at its exterior or interior for providing uniform diffuse
illumination of a substrate. An optic and imaging system exterior
of the light diffuser are used to inspect the plurality of surfaces
of the substrate including specular surfaces. The optic can be
rotated radially relative to a center point of the substrate edge
to allow for focused inspection of all surfaces of the substrate
edge.
Inventors: |
Jin; Ju (Austin, TX), Sadam;
Satish (Round Rock, TX), Verma; Vishal (Austin, TX),
Huang; Zhiyan (Austin, TX), Lin; Siming (Austin, TX),
Robbins; Michael D (Round Rock, TX), Forderhase; Paul F.
(Austin, TX) |
Assignee: |
Accretech USA, Inc. (Bloomfield
Hills, MI)
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Family
ID: |
40342102 |
Appl.
No.: |
11/891,657 |
Filed: |
August 9, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080030731 A1 |
Feb 7, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11417297 |
May 2, 2006 |
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Current U.S.
Class: |
356/237.4;
356/237.2; 356/237.6; 356/417; 356/446 |
Current CPC
Class: |
G01N
21/4738 (20130101); G01N 21/9503 (20130101) |
Current International
Class: |
G01N
21/00 (20060101) |
Field of
Search: |
;356/237.2-237.6,417,369,446 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 001 460 |
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May 2000 |
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EP |
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2000-136916 |
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May 2000 |
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JP |
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2003-243465 |
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Aug 2003 |
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JP |
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2006-294969 |
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Oct 2006 |
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JP |
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Other References
Article printout from Micromagazine.com website entitled "Reducing
Edge and Bevel Contamination to Help Enhance copper Process Yields"
dated Oct. 2000. cited by other .
Article printout from Micromagazine.com website entitled "Meeting
Manufacturing Metrology Challenges at 90 nm and Beyond" believed to
be dated Aug. 2005. cited by other .
Article printout from Solid State Technology entitled
"Implementation of CVD low-k Dielectrics for High-volume
Production" believed to be dated Jan. 2004. cited by other .
Article entitled "Edge and bevel automated defect inspection for
300mm production wafers in manufacturing" believed to be published
in Advanced Semiconductor Manufacturing Conference and Workshop,
2005 IEEE/SEMI Apr. 2005. cited by other .
Article in Semiconductor International entitled "The Wafer's Edge"
dated Mar. 2006. cited by other .
Article from Augusttech.com entitled "Advanced Macro Inspection
Provides Data to Address Blister Defects" believed to be dated Feb.
2005. cited by other .
Article from NCCAVS User Groups 2005 Annual Symposium entitled
"Plasma Etch Polymer: When Good Polymer Goes Bad" dated Oct. 2005.
cited by other.
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Primary Examiner: Lauchman; L. G
Assistant Examiner: Alli; Iyabo S
Attorney, Agent or Firm: Harness, Dickey & Pierce,
P.L.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent
application Ser. No. 11/417,297, filed on May 2, 2006, entitled
"Substrate Illumination and Inspection System". The disclosure of
the above application is incorporated herein by reference.
Claims
What is claimed is:
1. An automatic wafer edge inspection and review system comprising:
an illuminator configured to provide diffused illumination across
the top near edge surface, top bevel, apex, bottom bevel, and
bottom near edge surface; an optical imaging subsystem to image a
portion of the wafer edge; a positioning assembly to orientate the
optical imaging subsystem to an inspection angle; an eccentricity
sensor to actively measure the center offset of a wafer edge
relative to the rotation center of the wafer chuck; and a wafer
chuck to hold the backside of a wafer.
2. The system of claim 1, wherein the optical imaging subsystem
further comprises: an optical filter to cut off certain wavelength
spectrum; a mirror; an objective lens; a motorized focus lens to
provide routine-defined focus adjustment; a motorized zoom lens; a
magnifier lens; and a high resolution area scan color camera to
image a portion of the wafer edge.
3. The system of claim 1, wherein the illuminator comprises: a
cylindrical light diffuser having a slit extending at least a
portion of its length for receiving an edge portion of a wafer; a
plurality of light sources exterior or interior to the cylindrical
light diffuser; and an intensity controller for independently
controlling the plurality of light sources.
4. The system of claim 1, wherein the optical imaging subsystem is
orientated in such a way that its principal axis is always kept
away from the normal direction of the wafer edge portion under
inspection.
5. The system of claim 1 further comprising: a rotary stage which
rotates the wafer in a step-and-stop fashion; and a control console
to provide tool control functions, image display, defect
inspection, defect classification and edge exclusion measurement
capabilities.
6. The system of claim 5, wherein the eccentricity sensor measures
the eccentricity of a wafer and provides a signal to the control
console.
7. The system of claim 5, wherein the rotary stage rotates the
wafer along the circumference direction in a step-and-stop
manner.
8. The system of claim 6, wherein the linear stage performs the
eccentricity compensation, and brings the wafer to a best focus
position based on the signal from the eccentricity sensor.
9. The system of claim 5, wherein the control console performs
automatic defect inspection and classification, automatic
measurement of edge bead removal cut lines and semi-automated
defect review.
10. The system of claim 2, wherein the filter is a polarizer.
11. An automatic wafer edge inspection and review system of claim
1, wherein the wafer chuck is a pin-chuck and the wafer is held on
top of a plurality of pins by vacuum.
12. A wafer edge illumination and inspection system comprising: a
light diffuser having a slit extending at least a portion of its
length for receiving a portion of a wafer including a portion of
the wafer edge; a plurality of light sources in proximity to the
light diffuser; and an optical imaging subsystem for viewing the
wafer wherein the optic is exterior of the light diffuser, and is
positioned at an angle off a wafer edge surface normal, wherein the
optical imaging subsystem further comprises an optical filter to
cut off certain wavelength spectrum, a mirror, an objective lens, a
motorized focus lens to provide routine-defined focus adjustment, a
motorized zoom lens, a magnifier lens, a rotation mechanism for
rotating the optic about an axis parallel to the wafer radially
relative to a center point of the wafer edge region to allow
imaging of a wafer top near edge surface, top bevel, apex, bottom
bevel and bottom near edge surface, and a high resolution area scan
color camera to image a portion of the wafer edge.
13. The wafer edge illumination and inspection system of claim 12
further comprising: an illumination control system for
independently controlling the plurality of light sources.
14. The wafer edge illumination and inspection system of claim 12,
wherein the light diffuser is a quartz tube.
15. The wafer edge illumination and inspection system of claim 12,
wherein the plurality of light sources is an LED matrix.
16. The LED matrix of claim 15, wherein each LED is independently
controllable.
17. The wafer edge illumination and inspection system of claim 12,
wherein the plurality of light sources is an array of fiber optics
each coupled to an independent remotely located lamp.
18. The array of fiber optics of claim 17, wherein each lamp is
independently controllable.
19. The wafer edge illumination and inspection system of claim 12,
wherein the plurality of light sources is an LCD matrix.
20. The wafer edge illumination and inspection system of claim 12,
wherein the plurality of light sources is a flexible OLED.
21. A substrate imaging system for imaging a specular surface of a
substrate, the system comprising: a light diffuser housing having
an opening for receiving a portion of the substrate wherein the
interior of the light diffuser housing is a uniform neutral
background to a specular surface being imaged wherein the light
diffuser housing extends from over a top surface of the wafer to
adjacent an edge of the wafer and under a bottom surface of the
wafer; an optical subsystem angled off a surface normal of the
substrate area to be imaged wherein the optical lens is exterior to
the light diffuser, wherein the optical subsystem comprise, a
mirror, an objective lens, a motorized focus lens to provide
routine-defined focus adjustment, a motorized zoom lens to provide
both inspection and review functions, a magnifier lens, and a high
resolution area scan color camera to image a portion of wafer edge;
a light source disposed in the light diffuser housing; and an
eccentricity sensor to actively measure the center offset of a
wafer edge relative to the rotation center of the wafer chuck.
22. The substrate imaging system of claim 21, wherein the light
source is coupled to a fiber optic for directing light from the
light source to a plurality of locations of the light diffuser
housing.
23. The substrate imaging system of claim 21, wherein the light
source is one selected from the group of an LED matrix, LCD matrix,
and OLED.
24. The substrate imaging system of claim 21 further comprising: a
light controller for controlling the color and brightness of the
light source.
25. The substrate imaging system of claim 15, wherein the light
source is one selected from the group of an LED matrix, LCD matrix,
and OLED, wherein the light diffuser housing is a covering attached
to the light source.
Description
FIELD
The present disclosure relates to illumination and inspection of a
substrate, particularly illumination and inspection of specular
surfaces of a silicon wafer edge with diffuse light from a
plurality of light sources for enhanced viewing of the wafer
edge.
BACKGROUND
The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
Substrate processing, particularly silicon wafer processing
involves deposition and etching of films and other processes at
various stages in the eventual manufacture of integrated circuits.
Because of this processing, contaminants, particles, and other
defects develop in the edge area of the wafer. This includes
particles, contaminants and other defects such as chips, cracks or
delamination that develop on edge exclusion zones (near edge top
surface and near edge back surface), and edge (including top bevel,
crown and bottom bevel) of the wafer. It has been shown that a
significant percentage of yield loss, in terms of final integrated
circuits, results from particulate contamination originating from
the edge area of the wafer causing killer defects inside the FQA
(fixed quality area) portion of the wafer. See for example, Braun,
The Wafer's Edge, Semiconductor International (Mar. 1, 2006), for a
discussion of defects and wafer edge inspection methodologies.
Attempts at high magnification inspection of this region of the
wafer have been confounded by poor illumination of these surfaces.
It is difficult to properly illuminate and inspect the edge area of
an in-process wafer. An in-process wafer typically has a reflective
specular ("mirror") surface. Attempts at illuminating this surface
from a surface normal position frequently results in viewing
reflections of surrounding environment of the wafer edge thus
making it difficult to visualize defects or distinguish the defects
from reflective artifact. Further, the wafer edge area has a
plurality of specular surfaces extending from the near edge top
surface across the top bevel, the crown, the bottom bevel to the
near edge bottom surface. These too cause non-uniform reflection of
light necessary for viewing the wafer edge area and defect
inspection. In addition, color fidelity to observed films and
contrast of lighting are important considerations for any wafer
edge inspection system.
Therefore, there is a need for a system that adequately illuminates
the edge area of a wafer for inspection. It is important that the
system provide for illumination and viewing suitable for a highly
reflective surface extending over a plurality of surfaces and for a
variety of defects to be observed. The system must provide for
efficient and effective inspection of the edge area for a variety
of defects.
SUMMARY
Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
The object of the present invention is to provide a color
image-based edge defect inspection and review system. It comprises
an illuminator to provide uniform diffused illumination across the
five wafer edge regions: top near edge surface, top bevel, apex,
bottom bevel and bottom near edge surface, an optical imaging
subsystem to image a portion of wafer edge supported by a wafer
chuck, a positioning assembly to orientate the optical imaging
subsystem to the user-defined inspection angle, an eccentricity
sensor to actively measure the center offset of a wafer relative to
the rotation center of the wafer chuck, a wafer chuck to hold the
backside of a wafer onto the supporting pins, a linear stage to
move a wafer from its load position to the inspection position, a
rotary stage rotates the wafer in a step-and-stop fashion, a
control console to provide tool control functions as well as at
least the following capabilities: 1) automatic capture of defects
of interest with enough sensitivity and speed, 2) automatic defect
detection and classification, 3) automatic measurement of wafer
edge exclusion width; and 4) automatic report of inspection results
to the yield management system of a semiconductor fabrication
plant.
In accordance with the present disclosure, a substrate illumination
system has a light diffuser with an opening extending at least a
portion of its length for receiving an edge of a wafer. The system
also comprises a plurality of light sources in proximity to the
light diffuser. The system further comprises an optic for viewing
the wafer wherein the optic is exterior of the light diffuser and
is angled off of the wafer edge surface normal position.
In an additional aspect, the system comprises an illumination
control system for independently controlling the plurality of light
sources. Individually or by groups or sections, the plurality of
lights can be dimmed or brightened. In addition, the plurality of
lights can change color, individually or by groups or sections. Yet
another aspect of the system comprises a rotation mechanism for
rotating the optic from a position facing the top of the wafer to a
position facing the bottom of the wafer. In an additional aspect of
the system, the plurality of light sources is an LED matrix or
alternatively a flexible OLED or LCD. In this aspect the flexible
OLED or LCD can act in place of the plurality of lights or in place
of both the light diffuser and the plurality of lights. The light
sources can also be one or more halogen lamps. The one or more
halogen lamps can be coupled to an array of fiber optics.
In yet an additional aspect, the system comprises a method for
imaging the specular surface of a substrate. This method comprises,
isolating a portion of the substrate in a light diffuser, emitting
light onto the specular surface to be imaged and imaging the
specular surface with an optic positioned at an angle off the
specular surface normal from a position exterior to the light
emitter.
DRAWINGS
The drawings described herein are for illustration purposes only
and are not intended to limit the scope of the present disclosure
in any way.
FIG. 1 shows a schematic top view of the substrate illumination
system of the present disclosure;
FIG. 2 shows a schematic side view of the system as shown in FIG.
1;
FIG. 3 shows a detailed view of a portion of the view shown in FIG.
2;
FIG. 4 shows a schematic side view of an alternative embodiment of
the substrate illumination system;
FIG. 5 shows a detailed view of a portion of the view shown in FIG.
4;
FIG. 6 shows a schematic side view of another alternative
embodiment of the substrate illumination system;
FIG. 7 shows a perspective view of yet another embodiment of the
substrate illumination system; and
FIG. 8 shows a top plan view of the alternative embodiment of the
substrate illumination system as shown in FIG. 7;
FIG. 9 shows a perspective view of a wafer edge inspection and
review system of the present disclosure;
FIG. 10 shows a cross section view of the illuminator shown in FIG.
9;
FIG. 11 shows a enlarged cross section view of the wafer edge
regions;
FIG. 12 shows a schematic view of the optical imaging subsystem
shown in FIG. 9;
FIG. 13 shows the inspection angles of the optical imaging
subsystem shown in FIG. 9;
FIG. 14 shows the angle between the principal axis of the optical
imaging subsystem and the normal of the edge portion;
FIG. 15 illustrates the step-and-stop angular motion of a
wafer;
FIG. 16 shows a user interface for semi-automated defect
review;
FIG. 17 shows the process to review a specific defect of interest;
and
FIGS. 18 and 19 show an example of edge exclusion measurement.
DETAILED DESCRIPTION
The following description is merely exemplary in nature and is not
intended to limit the present disclosure, application, or uses. It
should be understood that throughout the drawings, corresponding
reference numerals indicate like or corresponding parts and
features.
Referring to FIGS. 1, 2, and 3 a substrate illumination system 10
(the "system") of the disclosure has a diffuser 12 with a slot 14
along its length and a plurality of lights 16 surrounding its
exterior radial periphery. Exterior of the diffuser 12 is an optic
18 that is connected to an imaging system 20 for viewing a
substrate 22 as the substrate is held within the slot 14. The
plurality of lights 16 are connected to a light controller 34.
The system 10 can be used to uniformly illuminate for brightfield
inspection of all surfaces of an edge area of the substrate 22
including, a near edge top surface 24, a near edge bottom surface
26, a top bevel 28, a bottom bevel 30 and a crown 32.
The optic 18 is a lens or combination of lenses, prisms, and
related optical hardware. The optic 18 is aimed at the substrate 22
at an angle off a surface normal to the crown 32 of the substrate
22. The angle of the optic 18 advantageously allows for preventing
a specular surface of the substrate 22 from reflecting back the
optic 18 whereby the optic 18 "sees itself." The viewing angle is
typically 3 to 6 degrees off normal. Some optimization outside of
this range is possible depending on illuminator alignment relative
to the substrate 22 and the specific optic 18 configuration.
The imaging system 20 is for example a charge-coupled device (CCD)
camera suitable for microscopic imaging. The imaging system 20 may
be connected to a display monitor and/or computer (not shown) for
viewing, analyzing, and storing images of the substrate 22.
Diffuser 12 is formed of a translucent material suitable for
providing uniform diffuse illumination. The diffuser 12 may be
formed of a frosted glass, a sand blasted quartz or a plastic or
the like, where light passing through it is uniformly diffused. In
a preferred embodiment, the diffuser 12 is a circular cylinder as
illustrated. Diffuser 12 may be an elliptic cylinder, generalized
cylinder, or other shape that allows for surrounding and isolating
a portion of a substrate 22 including the substrate 22 edge. The
slot 14 in the diffuser 12 extends for a suitable length to allow
introduction of the substrate 22 into the diffuser 12 far enough to
provide uniform illumination of the edge area and to isolate the
edge area from the outside of the diffuser 12.
Importantly, the interior of the diffuser 12 serves as a uniform
neutral background for any reflection from the specular surface of
the substrate 22 that is captured by the optic 18. Thus, the optic
18 while looking towards focal point F on the specular surface of
the crown 32 images (sees) the interior of the diffuser 12 at
location I. Similarly, the optic 18 looking towards focal points F'
and F'' on the specular surfaces of the top bevel 28 and bottom
bevel 30 respectively, images the interior of the diffuser 12 at
locations I' and I''.
The angle of the optic 18 in cooperation with the diffuser 12
prevents reflective artifacts from interfering with viewing the
plurality of specular surfaces of the edge area of the substrate
22. Instead, and advantageously, a uniform background of the
diffuser 12 interior is seen in the reflection of the specular
surfaces of the substrate 22.
The plurality of lights 16 is a highly incoherent light source
including an incandescent light. In a preferred embodiment, the
plurality of lights 16 is an array of LEDs. Alternatively, a quartz
halogen bulb can be the light source with fiber optics (not shown)
used to distribute light of this single light source radially
around the diffuser 12. In another preferred embodiment the
plurality of lights 16 is an array of fiber optics each coupled to
an independent, remotely located quartz tungsten halogen (QTH)
lamp.
The plurality of lights 16 is preferably a white light source to
provide the best color fidelity. In substrate 22 observation, color
fidelity is important because of film thickness information
conveyed by thin film interference colors. If the substrate 22
surface is illuminated with light having some spectral bias, the
thin film interference information can be distorted. Slight amounts
of spectral bias in the light source can be accommodated by using
filters and/or electronic adjustment (i.e., camera white
balance).
In operation, a substrate 22, for example, a wafer is placed on a
rotatable chuck (not shown) that moves the edge of the wafer into
the slot 14 of the diffuser 12. The light controller 34 activates
in suitable brightness the plurality of lights 16 for providing
uniform illumination of the edge area of the wafer. The wafer is
viewed through the imaging system 20 via the optic 18 and inspected
for defects. The wafer may be automatically rotated or manually
rotated to allow for selective viewing of the wafer edge. Thus,
observation of the wafer edge for defects is facilitated and is
unhindered by a specular surface of the wafer.
With added reference to FIGS. 4 and 5, in an embodiment of the
system 10 the plurality of lights 16 are individually controlled by
the light controller 34. In this embodiment light controller 34 is
a dimmer/switch suitable for dimming individually or in groups a
plurality of lights. Alternatively, light controller 34 can be the
type as disclosed in U.S. Pat. No. 6,369,524 or 5,629,607,
incorporated herein by reference. Light controller 34 provides for
dimming and brightening or alternatively turning on/off
individually or in groups each of the lights in the plurality of
lights 16.
The intensity of a portion of the plurality of lights 16 is dimmed
or brightened to anticipate the reflective effect of specular
surfaces that are inherent to the substrate 22, particularly at
micro locations along the edge profile that have very small radii
of curvature. These micro locations are the transition zones 33
where the top surface 24 meets the top bevel 28 and the top bevel
meets the crown 32 and the crown meets the bottom bevel 30 and the
bottom bevel 30 meets the bottom surface 26.
An example of addressable illumination is illustrated in FIGS. 4
and 5 where higher intensity illumination 36 is directed to a top
bevel 28, crown 32 and bottom bevel 30 while lower intensity
illumination 38 is directed to the transition zones 33 in between.
With this illumination configuration, the image of these transition
zones 33 are seen illuminated with similar intensity as compared to
the top bevel 28, crown 32 and bottom bevel 30.
Further, addressable illumination is useful to accommodate
intensity variation seen by the optic 18 due to view factor of the
substrate 22 edge area. Some portions of the substrate 22 edge area
have a high view factor with respect to the illumination from the
diffuser 12 and consequently appear relatively bright. Other
portions with low view factor appear relatively dark. Addressable
illumination allows mapping an intensity profile onto the wafer
surface that allows for the view factor variation and provides a
uniformly illuminated image. The required intensity profile can
change with viewing angle change of the optic 18.
Addressability of the illumination or its intensity can be
accomplished in a number of ways. One embodiment is to locate
independently controllable light-emitting diodes (LEDs) around the
outside of the diffuser 12 consistent with the plurality of lights
16. Another alternative is to employ a small flexible organic
light-emitting diode (OLED), liquid crystal display (LCD) or other
micro-display module. Such modules are addressable to a much
greater degree than an LED matrix. In this embodiment the flexible
OLED, LCD or other micro-display module can replace both the
plurality of lights 16 and the diffuser 12. For example, a flexible
OLED can both illuminate and have a surface layer with a matte
finish suitable for acting as a diffuser and neutral background for
imaging. Further, the flexible OLED can be formed into a suitable
shape such as a cylinder. Examples of a suitable OLED are disclosed
in U.S. Pat. Nos. 7,019,717 and 7,005,671, incorporated herein by
reference.
Further, those modules can also provide programmable illumination
across a broad range of colors including white light. Color
selection can be used to highlight different thin films and can be
used in combination with part of an OLED, for example, emitting one
color while another part of the OLED emits another color of light.
In some cases it can be beneficial to use only part of the light
spectrum, for example, to gain sensitivity to a film residue in a
given thickness range. This is one mode of analysis particularly
applicable to automatic defect classification. One analysis
technique to detect backside etch polymer residue preferentially
looks at light reflected in the green portion of the spectrum.
Thus, this embodiment of the system 10 provides for a suitable
color differential based inspection of the substrate 22.
Now referring to FIG. 6, in another embodiment of the system 10,
the optic 18 is rotatable in a radial direction 40 around the
substrate 22 at a maintained distance from a center point of the
substrate 22 edge. The optic 18 is rotatable while maintaining the
angle of the optic 18 relative to surface normal of the substrate
22 edge. This allows for focused imaging of all regions of the
substrate 22 surface, including the top surface 24, bottom surface
26, top bevel 28, bottom bevel 30 and crown 32. The rotating optic
18 can also include the imaging system 20 or consist of a lens and
a CCD camera combination or can be a subset of this consisting of
moving mirrors and prisms. This embodiment provides the additional
advantage of using one set of camera hardware to view the substrate
22 rather than an array of cameras.
Now referring to FIGS. 7 and 8, in another embodiment of the system
10, the optic 18 includes a fold mirror 50 and a zoom lens assembly
52. The optic 18 is connected to a rotatable armature 54 for
rotating the optic 18 radially around the edge of the substrate 22
(as similarly discussed in relation to FIG. 6). The substrate 22 is
retained on a rotatable chuck 56. The diffuser 12 is housed in an
Illumination cylinder 58 that is retained on a support member 60
connected to a support stand 62.
The operation of this embodiment of the system 10 is substantially
the same as described above with the additional functionality of
radially moving the optic 18 to further aid in inspecting all
surfaces of the edge of the substrate 22. Further, the substrate 22
can be rotated either manually or automatically by the rotatable
chuck 56 to facilitate the inspection process.
Referring to FIG. 9 an automatic wafer edge inspection and review
system 10 consists of an illuminator 11, an optical imaging
subsystem 64, a wafer supporting chuck 66 (not shown), a
positioning assembly 68, an eccentricity sensor 70, a linear stage
72, a rotary stage 74, and a control console 76. The eccentricity
sensor 70 is used to provide eccentricity data to the controller to
allow the controller to positionally adjust the substrate 22 with
respect to the imaging system 64. Optionally, data from the
eccentricity sensor 70 can be used to adjust the optics system to
ensure uniformity of the image and focus as opposed to or in
conjunction with the supporting chuck 66.
Referring to FIG. 10 and as described above, the illuminator 11
provides uniform illumination across the five wafer edge regions:
top near edge surface 78, top bevel 80, apex 82, bottom bevel 84,
and bottom near edge surface 86, as show in FIG. 11. It is also
envisioned the illuminator 11 can vary the intensity or color of
the illumination depending upon the expected defect or substrate
region. Additionally, the illuminator 11 can individually
illuminate different regions of the wafer. The light controller
received input from the system controller 76.
Referring to FIG. 12, the optical imaging subsystem 64 has a filter
121, a mirror 122, an attachment objective lens 123, a motorized
focus lens 124, a motorized zoom lens 125, and a magnifier lens
126, and a high resolution area scan color camera 127. The
motorized focus lens 124 automatically or manually sets best focus
position before starting automatic inspection and during the review
process. The filter 121 can be a polarizer, or optical filter which
allows the passage of predetermined frequencies.
The motorized zoom lens 125 can be configured in the low
magnification range for inspection purpose and high magnification
range for review purpose. As shown in FIG. 14, the positioning
assembly 68 orientates the optical imaging subsystem 64 to the
predefined inspection angle 51. To improve the image, the optical
imaging subsystem 64 is orientated in such a way that its principal
axis 128 preferably is kept from the normal direction 191 of the
wafer edge portion under inspection. The linear stage 72 moves the
wafer from its load position to the inspection position, and also
performs the eccentricity compensation to bring the wafer always to
the best focus position during the image acquisition period. While
the rotary stage 74 rotates the substrate 22 along the
circumference direction in a step-and-stop manner, as shown in FIG.
15, it is envisioned a continuous rotation of the wafer is
possible.
The control console 76 controls the system 10 via the tool control
software. In this regard, the console 76 controls the motion of
linear stage 72 and rotary stage 74, positioning the assembly 68 to
the user-defined inspection angle. The controller further presets
the magnification of the motorized zoom lens 125 and focus position
of the motorized focus lens 124, initializing the image acquisition
timing and other essential functions to complete the automatic
inspection of a wafer using user-predefined routines. The control
console 76 also displays the acquired images and runs the defect
inspection and classification software, reporting the results files
to a factory automation system.
Referring generally to FIG. 9 which shows the operation of one
embodiment, a substrate 22 is picked up from a FOUP (not shown) or
an open cassette (not shown) in the equipment front end module (not
shown) by the transportation robot arm 27, placed onto the
rotational table of the aligner (not shown). The aligner detects
the center of the substrate 22 as well as its notch, aligns the
wafer to the center axis of the rotational table. After alignment
is completed, the transport robot arm 27 picks up the substrate 22
from the aligner, places it onto the wafer chuck (not shown) of the
inspection and review system 10.
Then, the wafer is rotated and the eccentricity sensor 70 starts to
measure the eccentricity of the wafer relatively to the spin center
of the rotary stage 74. The eccentricity information is fed back to
the control console 76. At the same time, the positioning assembly
68 moves the optical imaging subsystem 64 to the routine inspection
angle. Then the linear stage 72 moves the substrate 22 to the
inspection position from the load position. The rotary stage 74
starts to move forward one step (routine-defined angle) and stops
completely. The illuminator 11 is turned on, and the camera 127
takes an image of the portion of the wafer edge within the field of
view of the optical imaging system 64. After completion, the rotary
stage 74 rotates one more step, settling down completely. The
linear stage 72 moves the substrate 22 to the best focus position
based on the eccentricity data stored in the control console 76.
During the movement of the stage 72, the control console 76
downloads the previous images from the camera to the onboard memory
and the hard disk media. Then, the camera 127 takes the second
picture of the wafer edge. The above steps are repeated until the
region of interest or the whole circumference of the substrate 22
is imaged.
If the system is set to inspect the edge regions of substrate 22 in
more than one inspection angles, the control console 76 moves the
positioning assembly 68 to another inspection angle, repeating the
steps described above. The images of the edge of the substrate 22
at the new inspection angle are recorded until all inspection
angles of interest are covered.
After the completion of imaging all the predefined edge regions of
substrate 22, the transport robot arm 27 picks the substrate 22
from the inspection chamber, and place it back to a FOUP or a
cassette in the equipment front end module.
While the system 10 takes pictures of the edge of substrate 22, the
inspection and classification software installed in control console
76 processes the raw images, detects the defects of interest,
classifies them into different classes or category and outputs to
the results files. To review a specific defect found by the system
10, the location and the inspection angle of the specific defect
can be retrieved from the results files. As shown in FIG. 16, an
operator inputs this information to the review system setup area of
tool control software in the control console 76. The control
console 76 automatically moves the substrate 22 and the positioning
assembly 68 to the predetermined positions, locates the specific
defect of interest. Then, the user adjusts the magnification of the
motorized zoom lens 125 to the desired value, focusing on the
defect by adjusting the position of the motorized focus lens 124.
The operator can now review the details of the defect on the
display and record its image to storage devices of the control
console 76.
Referring to FIGS. 9 and 18, the system is used to measure the cut
line 141 of the edge bead removal of a film layer 140. The
positioning assembly 68 moves the optical imaging subsystem 64 and
the area scan camera 127. In this position, the top near edge
surface of the substrate 22 with the cut line 141 is visible within
the field of view. The motorized focus lens 124 is set to the
position where the image is under best focus. The rotary stage 74
starts to move forward one step (predefined angle) and stops
completely. The illuminator 11 is turned on, and the camera 127
takes an image of a portion of the near top edge surface including
the cut line 141. Then, the rotary stage 74 moves one more step,
settling down completely. While the stage is in motion, the control
console 76 downloads the image from the camera 127 to the onboard
memory and the hard disk media. Upon completion, the camera 127
takes the second picture. The above steps are repeated until the
whole cut line along the circumference of the substrate 22 is
completely imaged and recorded onto onboard memory and the hard
disk media.
During operation, the control console 76 processes the recorded
images to calculate the profile of the cut line 141 as well as the
following parameters: the center disposition from the wafer center,
mean edge exclusion distance, the standard deviation, and the
peak-to-peak variation. The results are output to the results file
with predefined format.
As shown in FIGS. 9 and 19, the wafer edge inspection and review
system 10 can be used to measure multiple cut lines, for example,
151, 152, and 153 of multiple film layers 154,155, and 156. The
positioning assembly 68 moves the optical imaging subsystem 64 and
the area scan camera 127 to a position so that the top near edge
surface of the substrate 22 with the cut lines 151, 152 and 153 is
within the field of view. The motorized focus lens 124 is set to
the position where the image is under best focus. The rotary stage
74 starts to move forward one step and stops completely. The
illuminator 11 is turned on, and the camera 127 takes an image of a
portion of the near top edge surface including the cut lines 151,
152 and 153. Then, the rotary stage 74 moves a second step,
settling down completely. While the rotary stage is in motion, the
control console 76 downloads the picture from the camera 127 to the
onboard memory and the hard disk media. Upon completion, the camera
127 takes the second picture. The above steps are repeated until
the whole cut lines along the circumference of the substrate 22 are
completed imaged and recorded onto onboard memory and the hard disk
media.
It should be appreciated that while the embodiments of the system
10 are described in relation to an automated system, a manual
system would also be suitable. This includes a hybrid
automated/manual inspection with automated or manual defect
classification as described in U.S. Provisional Patent Application
60/964,163, filed Aug. 9, 2007, entitled "Apparatus and Method for
Wafer Edge Defects Detection" and U.S. Provisional Patent
Application 60/964,149, filed Aug. 9, 2007, entitled "Apparatus and
Method for Wafer Edge Exclusion Measurement", both incorporated
herein by reference. This also includes automated inspection in
conjunction with automated wafer handling including robotic wafer
handling with wafers delivered via FOUP or FOSB.
Thus, a cost effective yet efficient and effective system is
provided for illuminating and inspecting the plurality of surfaces
of the edge area of a substrate 22 and providing high quality
imaging of the inspected surfaces while avoiding the interference
associated with specular surfaces. The system provides for
improving quality control of wafer processing through edge
inspection with the intended benefit of identifying and addressing
defects and their causes in the IC manufacturing process with
resulting improvement in yield and throughput.
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